The invention relates to an overload detecting device of a bomb, and in particular relates to an overload test guard box of an air bomb. The overload test guard box provided by the invention solves the technical problems that the target box of an air bomb penetration test device is inconvenient to operate and use and the like. The overload test guard box provided by the invention comprises a base, a box body at the upper part and a guide rail arranged on the base, wherein a box body cover plate is arranged at the upper part of the box body; the box body comprises the front box body, the middle box body and the back box body; a muzzle guard plate and a bomb carrier baffle are sequentially arranged in the front box body; a speed measuring hole is formed at one side of the front box body; a slot which is installed with a target plate is formed in the middle box body; a recycle barrel is arranged in the back box body; a positioning clamp slot and a roller are arranged at the lower part of the box body; a limit mechanism is arranged at the tail end of the base; and the limit mechanism is connected with the back box body. The design scheme provided by the invention has the characteristics that the overload guard box is strict, feasible and convenient and can be used for air bombs with different volumes, and has the advantages of good practical value, reliability in operability and accurate experimental result.